Paper mills which use sulfate and kraft pulping processes often generate large quantities of condensate streams containing undesirable compounds such as hydrogen sulfide, mercaptans, crude sulfate turpentine, methanol and red oil. Many of these compounds exhibit noxious odors even at extremely low concentrations and the presence of significant amounts of these compounds in the condensate detracts from the recyclability of the streams including use of the streams for wash water make-up. Accordingly, the condensate streams containing these compounds are not readily recyclable and often find little utility.
Because the aforementioned compounds which cause problems are present in the condensate at relatively low concentrations, it is difficult and expensive to further reduce the concentration of these compounds to a level which will not be deleterious. Existing methods which attempt to reduce the concentration of such compounds in condensate streams often result in increasing the sulfur content of the liquid and produce waste streams that permit too much soda carry-over through the wash step with an attendant economic penalty.
It is therefore an object of the invention to provide a cost effective method for treating paper mill condensate streams containing low concentrations of odorous compounds to enhance their recyclability for various uses including pulp washing.
Another object of the invention is to provide a process for reducing the amount of hydrogen sulfide and mercaptans in paper mill condensate streams.
Still another object of the invention is to provide a method for treating paper mill condensate streams without increasing the sulfur or chloride content thereof.